The present invention relates to power brooms, and more particularly to power brooms useful in removing gravel, dirt, dust, and other debris from flat roofs prior to recovering the roof with additional gravel and roofing sealant materials (e.g., asphalt).
In re-roofing buildings with flat, built-up roofs having a sealant (e.g., asphalt or the like) and an aggregate (e.g., gravel) covering the roof, it is highly desirable to remove all of the loose gravel and dirt thereby to insure that the new sealant material will properly seal with the prior roofing materials thereby to result in a watertight roof.
Traditionally, roofers had used hand brooms and shovels to clean the roof of loose gravel, dirt, and other debris prior to applying the new sealant materials. In recent years, power driven rotary brooms have been used to power sweep the roof. These power brooms did, in general, a better job dislodging loose gravel from the roof, but they created a considerable amount of airborne dust. Additionally, these prior power brooms required a considerable amount of hand labor to shovel the swept-up gravel and to remove the gravel from the roof.
To overcome the problems associated with prior art power brooms, vacuum dust and gravel collection systems were incorporated on prior power brooms. Typically, the power broom was enclosed within a housing or shroud so that only the lower portion of the rotating brush of the power broom contacted the roof and so that the swept-up dust and gravel would be contained within the shroud. A vacuum conveying system was connected to the shroud so as to vacuum convey the dust and gravel from the power broom as it moved across the roof. The vacuum conveying system generally consisted of a large vacuum source, such as a motor driven blower, mounted on a truck on the ground adjacent the building and connected to the power broom on the roof by means of a long, flexible hose. One such power vacuum broom is shown in U.S. Pat. No. 4,120,311.
However, while such prior art power vacuum brooms were quite effective in decreasing the amount of airborne dust, it was difficult for these prior art vacuum power brooms to entrain the dense gravel particles swept-up from the roof. Due to the high density of the gravel particles, very high air velocities within the shroud enclosing the power broom were required to be generated in order for the gravel particles to be entrained in the vacuum conveying airstream. If the vacuum source could not generate sufficiently high air velocities within the power broom shroud, gravel particles, particularly larger gravel particles, could accumulate within the power broom shroud thus requiring periodic and often shutdown of the power broom and manually cleaning certain areas with the broom enclosure.
Also, in prior art vacuum power brooms, very large clumps of dirt, gravel adhered to clumps of loosened asphalt, and other relatively large sized debris could be swept-up by the power broom, but would lodge in the vacuum conveying system thus blocking the flow of air through the vacuum system.
It will also be appreciated that in using a vacuum power broom on tall buildings or on buildings having a large roof, very long runs of hose (for example, 200-300 feet or more) were required to connect the power broom to the vacuum source located on the ground. Of course, these longer runs of hose resulted in an increased air flow friction within the hose which in turn reduced the air flow through the power broom and reduced the effectiveness of the broom in vacuum conveying the dense gravel particles. Also, these long runs of hose, when dragged across the roof, exerted a substantial force on the side of the power broom and made it difficult for the operator to accurately guide the power broom as it was propelled across the roof.
Also, in certain self-propelled power vacuum brooms, the drive wheels of the broom could be declutched or disengaged from the engine while the rotating brush was still being driven by the engine and while the brush was still in brushing or sweeping engagement with the roof. Thus, the rotating brush in contact with the roof resulted in a reaction driving force being applied to the power broom which tended to drive it in reverse direction. In certain instances, when the operator was standing next to the edge of the roof, this reverse driving action could dangerously push the operator backwards possibly causing him to fall from the roof, especially if the operator was not expecting the reverse propulsion force when he declutched the driving wheels.
Reference may be made to such prior U.S. patents as U.S. Pat. Nos. 485,577, 2,263,722, 3,676,886, 3,704,477 and 3,955,236 which disclose apparatus in the same general field as the present invention.